From a900580a665c2e1cf77a343c683e4baada63b69d Mon Sep 17 00:00:00 2001
From: paulfd <paulfd@outlook.fr>
Date: Sun, 15 Sep 2019 22:47:24 +0200
Subject: [PATCH] Added another subtract SIMD helper

---
 sfizz/SIMDDummy.cpp |  7 +++++++
 sfizz/SIMDHelpers.h | 17 +++++++++++++++++
 sfizz/SIMDSSE.cpp   | 20 ++++++++++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/sfizz/SIMDDummy.cpp b/sfizz/SIMDDummy.cpp
index 507c15d5..fd19d1c2 100644
--- a/sfizz/SIMDDummy.cpp
+++ b/sfizz/SIMDDummy.cpp
@@ -126,6 +126,13 @@ void subtract<float, true>(absl::Span<const float> input, absl::Span<float> outp
     subtract<float, false>(input, output);
 }
 
+template <>
+void subtract<float, true>(const float value, absl::Span<float> output) noexcept
+{
+    subtract<float, false>(value, output);
+}
+
+
 template <>
 void copy<float, true>(absl::Span<const float> input, absl::Span<float> output) noexcept
 {
diff --git a/sfizz/SIMDHelpers.h b/sfizz/SIMDHelpers.h
index db4de29e..6a9b2a90 100644
--- a/sfizz/SIMDHelpers.h
+++ b/sfizz/SIMDHelpers.h
@@ -374,6 +374,21 @@ inline void snippetSubtract(const T*& input, T*& output)
     *output++ -= *input++;
 }
 
+template <class T>
+inline void snippetSubtract(const T value, T*& output)
+{
+    *output++ -= value;
+}
+
+template <class T, bool SIMD = SIMDConfig::subtract>
+void subtract(const T value, absl::Span<T> output) noexcept
+{
+    auto* out = output.begin();
+    auto* sentinel = output.end();
+    while (out < sentinel)
+        snippetSubtract(value, out);
+}
+
 template <class T, bool SIMD = SIMDConfig::subtract>
 void subtract(absl::Span<const T> input, absl::Span<T> output) noexcept
 {
@@ -388,6 +403,8 @@ void subtract(absl::Span<const T> input, absl::Span<T> output) noexcept
 template <>
 void subtract<float, true>(absl::Span<const float> input, absl::Span<float> output) noexcept;
 
+template <>
+void subtract<float, true>(const float value, absl::Span<float> output) noexcept;
 
 template <class T>
 void snippetCopy(const T*& input, T*& output)
diff --git a/sfizz/SIMDSSE.cpp b/sfizz/SIMDSSE.cpp
index 63a11fa4..69b9fd07 100644
--- a/sfizz/SIMDSSE.cpp
+++ b/sfizz/SIMDSSE.cpp
@@ -564,6 +564,26 @@ void subtract<float, true>(absl::Span<const float> input, absl::Span<float> outp
         snippetSubtract<float>(in, out);
 }
 
+template <>
+void subtract<float, true>(const float value, absl::Span<float> output) noexcept
+{
+    auto* out = output.begin();
+    auto* sentinel = output.end();
+    const auto* lastAligned = prevAligned(sentinel);
+
+    while (unaligned(out) && out < lastAligned)
+        snippetSubtract<float>(value, out);
+
+    auto mmValue = _mm_set_ps1(value);
+    while (out < lastAligned) {
+        _mm_store_ps(out, _mm_sub_ps(_mm_load_ps(out), mmValue));
+        out += TypeAlignment;
+    }
+
+    while (out < sentinel)
+        snippetSubtract<float>(value, out);
+}
+
 template <>
 void copy<float, true>(absl::Span<const float> input, absl::Span<float> output) noexcept
 {